proportioning valve?

[Gerry Holmes]

hi Guys, i'm just about finished my 383 Barracuda swap, but i'm having a brake problem. i got the car with a new master cylinder and power booster to fit a 1974 dart, the same as my K-frame and disks brakes that were on the car when i bought it. i also got a seperate proportioning valve (not sure if its from 1967 barracuda or 1974 dart). now i put on new hoses, calipers, pads, drums and shoes, and have everything bled (no air), but the the pedal goes to 2" from the floor and locks the rear brakes. if i put hose clamps on the front 2 lines to the calipers, the pedal only goes down 1", with the clamps off, back to the 2" off the floor. the front 2 calipers are putting out straight fluid, no air. here's my question, is this what would happen if the proportioning valve was the original 1967 Barracuda 4 drum valve, and not the 1974 dart 2 drum- 2 caliper valve, in other words, i'm not getting the correct proportion of fluid ( volume) to lock the calipers sooner. thanks for your help Gerry

 

[Robbie2734]

hi Guys, i'm just about finished my 383 Barracuda swap, but i'm having a brake problem. i got the car with a new master cylinder and power booster to fit a 1974 dart, the same as my K-frame and disks brakes that were on the car when i bought it. i also got a seperate proportioning valve (not sure if its from 1967 barracuda or 1974 dart). now i put on new hoses, calipers, pads, drums and shoes, and have everything bled (no air), but the the pedal goes to 2" from the floor and locks the rear brakes. if i put hose clamps on the front 2 lines to the calipers, the pedal only goes down 1", with the clamps off, back to the 2" off the floor. the front 2 calipers are putting out straight fluid, no air. here's my question, is this what would happen if the proportioning valve was the original 1967 Barracuda 4 drum valve, and not the 1974 dart 2 drum- 2 caliper valve, in other words, i'm not getting the correct proportion of fluid ( volume) to lock the calipers sooner. thanks for your help Gerry

I take it you are using the single piston calipers, so the next question is what size is the master cylinder bore? On my conversion I used the proportion valve from the 74 I got the disks from. You might try a larger bore MC, it will push more fluid for the same pedal travel. On the other point, I swore I bled all the air from mine, I didn't! Will the brakes pump up? I had to pull the calipers off the rotor and using a c clamp to hold the piston in, then hold the bleeder valve straight up and then bleed. I got more air out and the system then worked! The proportioning valve should match the master cylinder, I don't know how much effect it will have if mismatched.

 

[Gerry Holmes]

hi Robbie, just found out that the master cylinder, calipers and proportioning valve are all from a 1973 dart, so therefore they match. and no they will not pump up. thanks Gerry